Ce-modified Ni nanoparticles encapsulated in SiO2 were prepared, and used as efficient catalyst for COx-free hydrogen production via ammonia decomposition. Due to the introduction of an appropriate amount of Ce, the catalysts properties were altered by enhancing NiO dispersion and reducing NiO particle size with high-surface-area. And the catalysts are highly stable owing to the SiO2 shell preventing the enwrapped core particles from aggregation at high reaction temperature. High catalytic activity of the almost total conversion of ammonia at 650 degrees C with H-2 producing rate of 33.24 mmol g(cat)(-1)min(-1) is achieved on the prepared stable core-shell structured Ce-Ni@SiO2 catalysts, which is higher than Ce-NiO and Ni@SiO2 catalysts. Copyright (C) 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.